This patent application claims priority based on a Japanese patent application, H11-136214 filed on May 17, 1999, the contents of which are incorporated herein by reference.
1. Field of the Invention
The present invention relates to an electron beam tester, recording medium thereof and a signal data detecting method. More particularly, the present invention relates to the electron beam tester for testing an electric component, the recording medium which stores a program executed by the electron beam tester and the signal data detecting method of detecting data on a signal at a predetermined position of the electric component.
2. Description of the Related Art
In the conventional practice, for example, an electron beam tester is used for testing electric components such as a semiconductor memory and so on. The electron beam tester irradiates an electron beam to an electric component to be tested. Then, by detecting a secondary electron amount generated at the electric component, an electron image of a strobe image of the electric component and a voltage waveform at a predetermined position of the electric component are obtained.
FIGS. 1A, 1B and 1C are provided in order to explain a voltage waveform, obtained by the electron beam tester, at a predetermined position of the electric component. When a signal shown in FIG. 1A is supplied to a predetermined position of the electric component, a voltage waveform shown in FIG. 1A is supposed to be obtained by the electron beam tester. However, there are occasions where a voltage waveform which is unwantedly deformed with respect to the voltage waveform shown in FIG. 1A is obtained instead of the ideal voltage waveform shown in FIG. 1A. Reasons why such a deformed voltage waveform is obtained are considered to be those as shown in FIG. 1C when a signal given contains a signal whose period is displaced, that is, the given signal contains a jitter, or that a signal per se in the electric component is deformed.
However, in the conventional electron beam tester, a problem occurs where a tester cannot distinguish which one of the following actually causes the deformation of the voltage waveform. Namely, such possible two causal factors are:
(1) a signal given contains a jitter, or
(2) a signal per se in the electric component is deformed.
Moreover, recent years required are acquisition and detection of data on the signal at the electric component, such as the data on a voltage fluctuating amount of the signal and data on the phase of jitter in the case with the jitter being contained.
Therefore, it is an object of the present invention to provide an electron beam tester, recording medium and a signal data detecting method which overcome the above issues in the related art. This object is achieved by combinations described in the independent claims. The dependent claims define further advantageous and exemplary combinations of the present invention.
According to an aspect of the present invention, there is provided an electron beam tester for testing an electric component, the tester comprising: a drive circuit which supplies a signal to the electric component; an electron gun which causes to emanate a secondary electron from the electric component by irradiating the electron beam to a predetermined position of the electric component; a detector which detects an amount of the secondary electron emanated from the electric component; a first variation detecting unit which detects first variation data indicative of a magnitude of a variation amount of the secondary electron, based on the amount of the secondary electron detected by said detector at a predetermined position of the electric component, with a voltage of the secondary electron being constant; a second variation detecting unit which detects second variation data indicative of a magnitude of a variation amount of the secondary electron, based on the amount of the secondary electron detected by said detector at a predetermined position of the electric component, with a voltage fluctuation of the signal being indeterminate; and a voltage fluctuating data detecting unit which detects voltage fluctuating data indicative of a magnitude of voltage fluctuation when the voltage fluctuation of the signal is indeterminate.
In the electron beam tester where the drive circuit supplies to the electron component the signal having a predetermined period, and the voltage fluctuation of the signal is generated by a jitter in which the signal is displaced from the period, the electron beam tester may further comprise: an electron gun control unit comprising a first electron gun control section which instructs said electron gun to irradiate the electron beam synchronized with the first phase in which a voltage of the signal at the predetermined position stays fixed without being affected by the jitter; and a second electron gun control section which instructs said electron gun to irradiate the electron beam synchronized with a second phase in which a voltage of the signal at the predetermined position of the electric component fluctuates due to the jitter.
The first variation detecting unit detects a first variation data indicative of a magnitude of the secondary electron amount, based on the secondary electron amount detected by said detector as a result of the electron beam irradiated from the said electron gun by said first electron gun control section.
The second variation detecting unit detects a second variation data indicative of a magnitude of the secondary electron amount, based on the secondary electron amount detected by said detector as a result of the electron beam irradiated from said electron gun by said second electron gun control section.
The voltage fluctuating data detecting unit detects a magnitude of the voltage at the second phase due to the jitter, based on the first variation data and the second variation data.
The electron beam tester may further comprise: a driver which outputs a desired analysis voltage which serves to control the degree of the secondary electron taken in for detection, in a varying manner, said detector detecting the secondary electron taken in by the analysis voltage; a coincidence analysis voltage detecting unit which detects a coincidence analysis voltage that coincides with a reference secondary electron amount or a slice level set in advance; and a phase determining unit which determines the first phase and the second phase based on the coincidence analysis voltage.
The electron beam tester may further comprise: a driver output control unit which instructs the driver to output a same analysis voltage as the coincidence analysis voltage, at the first phase, detected by the coincidence analysis voltage detecting unit when the electron beam is irradiated from the electron gun by the first electron gun control unit, and which instructs the driver to output a same analysis voltage as the coincidence analysis voltage, at the second phase, detected by the coincidence analysis voltage detecting unit when the electron beam is irradiated from the electron gun by the second electron gun control section.
Moreover, the voltage fluctuating data detecting unit may detect the voltage fluctuating data by subtracting the first variation data from the second variation data.
Moreover, a plurality of phases may be used as the second phase.
The electron beam tester may further comprise a voltage fluctuating amount detecting unit which detects a voltage fluctuating amount due to the jitter at the second phase, based on the voltage fluctuating data.
Moreover, the voltage fluctuating amount detecting unit may detect the voltage fluctuating amount based on relationship between the analysis voltage at the second phase and the secondary electron amount detected by the detector.
The electron beam tester may further comprise a display unit which displays relationship between the voltage fluctuating amount and the second phase of the signal.
The electron beam tester may further comprise: a phase data detecting unit which detects phase data indicating a phase of the jitter, based on the voltage fluctuating amount; and a display unit which displays the phase data on the jitter.
The electron beam tester may further comprise a phase voltage detecting unit which detects a voltage of the signal at the phase at a predetermined position of the electric component, based on the coincidence analysis voltage detected by the coincidence analysis voltage detecting unit.
Moreover, the phase voltage detecting unit detects the phase data indicating a phase of the jitter, based on a voltage of the signal at the phase detected by the phase voltage detecting unit and the voltage fluctuating amount.
Moreover, the phase data detecting unit may detect the phase data indicating a phase of the jitter, based on the wave form obtained by adding to voltages of the signal at a plurality of phases detected by the phase voltage detecting unit the voltage fluctuating amount at the phase in question.
Moreover, the phase data detecting unit detects the phase data indicating a phase of the jitter, based on reference voltage change data which represent a relationship between a phase and a voltage fluctuation of a jitter-free reference signal, and the voltage fluctuating amount.
According to another aspect of the present invention there is provided a recoding medium storing an executable program in an electron beam tester comprising a drive circuit for supplying a signal to an electric component, an electron gun for causing to emanate a secondary electron from the electric component by irradiating an electron beam to a predetermined position of the electric component, and a detector for detecting an amount of the secondary electron emanated from the electric component, in which the program comprises: a first program which instructs to detect first variation data indicative of a magnitude of variation of the secondary electron amount, based on the secondary electron amount detected by the detector while a voltage of the signal stays fixed at the predetermined position of the electric component; a second program which instructs to detect second variation data indicative of a magnitude of variation of the secondary electron amount, based on the secondary electron amount detected by the detector while a voltage fluctuation of the signal is indeterminate at the predetermined position of the electric component; and a third program which instructs to detect voltage fluctuating data indicating a fluctuating magnitude of a voltage in the case of a voltage fluctuation of the signal being indeterminate, based on the first variation data and the second variation data.
According to still another aspect of the present invention, there is provided a method of detecting data on a signal at a predetermined position of an electric component when testing the electric components, the signal data detecting method comprising: (1) causing to emanate a secondary electron from the electric component by irradiating an electron beam to the predetermined position of the electric component; (2) detecting the secondary electron; (3) detecting first variation data indicative of a magnitude of the secondary electron, based on an amount of the secondary electron detected in said detecting the secondary electron in a case where a voltage of the signal at the predetermined position of the electric component stays fixed; (4) detecting second variation data indicative of a magnitude of the secondary electron, based on an amount of the secondary electron detected in said detecting the secondary electron in a case where a voltage fluctuation of the signal at the predetermined position of the electric component is indeterminate; (5) detecting voltage fluctuating data indicative of the voltage fluctuation in the case of the voltage of the signal being indeterminate thus containing a jitter, based on the first variation data and the second variation data.
This summary of the invention does not necessarily describe all necessary features of the present invention. The present invention may also be a sub-combination of the above-described features. The above and other features and advantages of the present invention will become more apparent from the following description of embodiments taken in conjunction with the accompanying drawings.